Resistance-adjusting device.



No. 870,042. PATENTED NOV. 5, 1907.

H. P. MAOLAGAN. RESISTANCE ADJUSTING DEVICE.

APPLIUATIOI FILED 00T.11l 1905.

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UNITED STATES PATENT OFFICE.

HECTOR P. MAC LAGAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO NATIONAL'RHEOSTAT COMPANY, OF CHICAGO, ILIJINOIS, A CORPORATION OF ARIZONATERRITORY.

RESISTANCE-mammina DEVICE.

Specification of Letters Patent.

Patented Nov. s, 1907.

Application led October 1l. 1905- Serial llo. 282.282.

To all 'whomy it may concern:

Be it known that I, Hnc'ron P. MAC LAGAN, acitizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Resistance-AdjustingDevices, of which the following is a full, clear, concise, and exactdescription, reference being had to the accompanying drawings, forming apart of this specification. i

My invention relates to adjustable resistancev de#- vices and moreparticularlyfto such devices to be used for the regulation of smallercurrent flow, .such as that fiow through voltmeters, galvanometers, orother like delicate instruments, and the object Aof the invention is toprovide a device which is of very-simple construetion and thereforeinexpensive, and which is more eliicient and reliable than devices of alike character.'

I am aware of ,prior devices for adjusting current` flow such as devicesin which carbon forms the resistance medium.. In these prior devices,however, the resistance conditions are not constant; that is, thecoefficient of the resistance is not sufficiently small, consequentlymaking such devices unreliable in the delicate class of work for whichthey are to be used. In my invention, however, the material used is Wirehaving a resistance coefficient which is practically zero and theresistance conditions for one position of the device will be practicallyconstant. i

The construction of. my device will appear best by reference to theaccompanying drawing, in which Figure 1 is a plan view, part of thecover thereof being removed, and Fig. 2 is a sectionaliview taken onlino 2 2 of Fig. 1. I I

The resistance medium of the deviceis composed of the wire 1 arranged toform the winding 2. This wire which is known on the market as I. A. I.A. wire, is o f a certain composition which renders the coefficientthereof practically zero and which renders it very hard and tough. Thewinding is of cylindrical formas shown, and the wire may be wound in anymanner about the core 3. The winding is best arranged, however, byhaving the core of some flexible material,l

such as paper, fiber, rubber or other flexible insulating material,which in its normal straight position is wound with the wire andsubsequently bent to assume the cylindrical shape as shown. To supportthe winding I provide a cylindrical core or block 4 also of insulatingmaterial, such as wood, and the winding core after ythe wires have beenplaced thereon yis bent around the cylindrical face 5 of the block torest against the flange 6 and is then secured in place by being glued tothe block, or, as shown, by means of screws or nails]l y7 driven throughthe core 3 into engagement with the block. The wire which is normallyunnsulated wound around the core to leave insulating space bea with theresistance wire.

tween the coils, and after the winding is completed I apply insulatingmaterial between the coils, and I preferably use a solution of silicateof soda, this being easily applied with a brush and which eventually I'hardens to almost the consistency of glass and thus also protectsthefwindings against mechanical injury. The core 3 may also be coveredwith a coating of this material before the -windings are applied. Fromthe center of the block extends a pivot post 8 to whichlis pivoted theadjusting lever mechanism for engagement The switch blade or Contactlever 9 for thisl mechanism is of springy material` and extends radiallyfrom the pivot post so that its end 10` may have pressing engagementalong the upper edge y l1 of the resistance winding, and as the switchlever '70 is rotated this end will travel successively over'the ends ofthe various winding coils. i

To actuate the switch blade I provide the actuating handle or lever 12secured with the switch lever to thev hub 13 to form a unitary structurewhichv is held in place on the pivot post by means of the pivot screw14. The switch lever and actuating lever are spaced so that with thecover 15 in position. the switch lever will be at the interior thereofand the actuating handle atl the outside thereof. This cover when inposition engages about the outer edge of the flange 6l and vmay besecured thereto by nails or screws 16. To apply the cover the screw 14is removed 'and the switch blade `and the lever frame and-the hub 13 canreadily-be slipped through the opening 17 throughthe cover, and 85 thescrewbeingthen again secured in position the device is ready for,operation and the parts thereof entirely inclosed-and protected.

Suitable terminal posts may be provided for the terminals 18 and 19 ofthe winding, but I have shown the terminal posts 2O and 2l extendingthrough themounting block to the base'thereof and are provided withthreaded openings 22 for' receiving threaded terminal pins. of leads.4The pivot post for tho'aetuating lever also extends through the mountingblock and is also provided with a threaded opening 23 for thereceptionof lead tips. One-terminal of the circuit for which theresistance is to be adjusted connects with the 'switch blade pivot post,and the other limb of the circuit by connection'to the terminals 20 and21 serially includes more or lessof the resistance winding, dependingupon the position of the switch blade with `respect thereto.

The insulating material, or sodium silicate in this case, f is notapplied to the edge 11 along which the end of and can be used for themost delicate work. The composition of the wire used renders theresistance con- I stant and the resistance in circuit remains constantfor along-one edge of the band.-

vice extremely useful and desirable when used in 0011-' nection withsuch delicate instruments as voltmeters, galvanometers, or the like. 'v

' I-do not'wish to be limited, however, to the precise arrangement and-treatment of the partsl as slio'wnand described,- as changes may,readily be madewithout departing from the spirit of the invention.

I claim as new, however, and desire to secure'by Letters Patent:

1. In a device ot the class described, the combination with a resistancewinding formed of a wirewound transversely around a band across theedges thereof, of a contact lever adapted for engagement with theadjacent turns 2. In a device of the class described, the combinationwith a resistance winding formed of wire wound transversely around thewall of a cylindrical shell and across the edges thereof, of a rotatablecontact lever pivoted at the center of said shell and having a contactfor' engagement with the ends of adjacent' coils along an edge of saidshell. 1

3. In a ydevice of the class described, the combination 'with acylindrical mounting block, of a resistance winding formed of wire woundtransversely around the wall of a cylindrical shell across the edgesthereof, said shell being mounted about the cylindrical face of theblock, and a ro tatabie `contact lever pivoted at'the center of said'block and having a contact for engaging the wire at the ends of.

adjacent coils along one edge of the shell.,

. 4. In a device of the class described, the combination with a windingformed of wire wound around the wall or' a cylindrical shell across theedges of the shell, of a contact lever pivoted at the center of saidshell and adapted upon rotation to engage the wire at the end of theadjacent coils along one edgeof the shell, an actuating lever for saidcontact lever, and a cover for said device disposed between theactuating and the contact levers whereby said actuating lever will be atthe outside of the cover and the contact lever at the inside of thecover.

5. In a deviceoi.` the class described, the combination with acylindrical mounting block, of a resistance coil in the'form of aflexible sheet wound transversely vwith wire across the edges thereofand subsequently bent cylindrically to be secured about the cylindricalsurface of the mounting block and engaging at its end with the end ofadjacent coils along one edge of the sheet, Athe end of the contact armupon rotation of the arm passing along the edge of the sheet intosuccessive engagement with the ends of adjacent coils. j

6. In a device of-the. class described, the combination with acylindrical mounting block,. of a resistance coil thereon, saidresistance coilA being in the. form of a continuous winding mounted on aflexible strip or ribbon subsequently bent into a cylindrical form tolit about the cylindrical edge of the mounting block, the upper edge ofsaid coil extending a slight distance above the mounting block, a leverpivoted at the center of the block, and a contact on said lever bearingagainst the upper edge of said winding, rotation of said lever causingsaid contact toibe carried over the edge of the winding into successivoengagement with'the coils thereof.

7. In a device of the class described, the combination with a resistancewinding wound with a non-insulated 8. In a device of the classdescribed, the combination with a resistance coil composed ofnon-insulated wire wound transversely over a flexible strip or ribbon ofinsulating material, adjacent coils being slightly separated and thestrip with the windings thereon being subsequently hentto form acylindrical shell, insulating vmaterial in the form of sodium silicateapplied between and on the winding to insulate the coils thereof and toprotecty them against mechanical injury, the top edge of the windingbeing left free from said insulating material, and a contact on saidlever pressed thereby against the edge of the winding of the coil,rotation of the lever causing the contact to be carried about said edgeinto successive engagement with the coils of the winding.

9. In a device of thev class described, the combination with acylindrical mounting block having -n horizontal flange at its'lower end,ofn resistance coil in the form of a continuous winding wound on aflexible strip or ribbon of insulating material subsequently bent in theform of a 4cylindrical shell and secured about the' cylindrical edge'4of the mounting block to rest on said-flange, the upper edge of saidcoil extending a distance` above thev mounting block, a pivot post atthe center of said mounting block, a lcontact arm pivoted to said pivotpost and engaging at its end on the upper edge of said winding, aseparate actuating handle pivoted to said pivot post and secured to theAContact lever, and an inclosing shell for the device adapted to bedisposed between the actuating lever and the contact lever vwhereby theactuating lever only will be at the exterior of the cov'er, said coverbeing secured about the cylin- Idrical edge of the flange.

10. An adjustableresistance device composed of a cylindrical mountingblock of insulating material, a cylindrical shell secured about themounting block, a resistance winding wound continuously about said shellto form transverse coils whose vertical edges are disposed to form acircular contact edge, an actuating arm pivoted at the center of themounting block, and a contact on said arm held in spring engagement withsaid resistance edge, rotation of said arm causing said contact to becarried about said edge in successive engagement` with the ends of thecoils composing said-edge.

1 1. An adjustable resistance device'composed of a cylindrical mountingblock of insulating material, aA cylindrical shell secured about themounting block, a resistance winding 'wound continuously about saidshell to form trans` verse coils whose vertical edges are disposed toform a circular contact edge, .an actuating armpivoted at the center ofthe mounting block, and a contact on said arm held in spring engagementwith said resistance edge, rota` tion of said arm causing said contactto be carried-about snidedge in successive engagement with the ends ofthe coils composing said edge, the wire forming the winding beingnormally uninsulated and wound to leave spaces between coils, saidspaces'being subsequently lled with insulating material. adapted toharden to maintain electrical separation of thecoils and to protect themagainst mechanical injury.

I 12. An adjustable resistance device composcdof a cylindrical mountingblock of insulating material, a cylindrical shell secured'about themounting block, a resistance winding wound continuously about said shellto form trans verse coils whose vertical edges are disposed to form acircular contact edge, an actuating arm pivoted at the center lof theinountingrblock, and a contact on said arm held in spring engagementwith said resistance edge, rotation of said arm causing said contact tobe carried about said edge in successive engagement with the ends of thecoils composing said edge, the cylindrical shell being normally inthe-form of a band or ribbon b y which the wire is wound andsubseduently bent with the wire thereon into the cylinv drical form.

In witness whereof, l hereunto subscribe my name this 9th day of OctoberA. D., 1905.

. Hnc'ron i. MAC LAGAN.

Witnesses:

CHARLES .I." SCHMIDT, LEONARD W. NovANnsn.

